The invention comprises improvements in a transaxle assembly of the kind disclosed in U.S. Pat. No. 4,509,389. That patent, which is assigned to the assignee of this invention, discloses a hydrokinetic transaxle for use in a front-wheel drive vehicle with the axis of the engine mounted transversely with respect to the center plane of the vehicle. The transmission comprises a three-element hydrokinetic torque converter on the engine axis and two simple planetary gear units mounted on the axis of the side gears of differential gearing on the torque output side of the transaxle.
The turbine of the torque converter of the '389 patent is connected by a torque transfer chain drive to torque input elements of the planetary gear units. The output element of the planetary gear units is connected to the torque input side of a final drive gear which transfers torque to the differential carrier of the differential gearing.
A lock-up clutch assembly in the hydrokinetic torque converter of the '389 patent establishes a fully mechanical torque transfer, when the clutch is engaged, between the engine and the turbine.
U.S. Pat. Nos. 4,633,738 and 4,665,770 disclose control systems capable of being used in a transaxle assembly of the kind disclosed in U.S. Pat. No. 4,509,389. The '738 patent and the '770 patent are also assigned to the assignee of this invention.
Each of the control systems disclosed in the '770 and '738 patents includes a fluid pressure governor valve assembly for establishing a fluid pressure signal representative of vehicle speed. They include also throttle valves of conventional kind which establish a control pressure that is a measure of engine throttle position or engine torque. Multiple shift valve assemblies respond to the signals to establish ratio changes as the clutches and brakes, which form a part of the planetary gear system, are engaged and released to satisfy driver demands and driving conditions.